UH Hilo, Canada-France-Hawaiʻi Telescope, and Université Laval Collaborate to Simulate Galaxy Collision

A new study co-authored by Camille Poitras, PhD student at Université Laval, Dr. R. Pierre Martin of the University of Hawaiʻi at Hilo (UHH), and colleagues at Université Laval in Québec, Canada, simulates the past, present, and future of a collision between two spiral galaxies. The authors relied on the “amazing” data from the Canada-France-Hawaiʻi Telescope (CFHT)’s Fourier transform spectrograph SITELLE — the only instrument of its kind in the world, based right here in Hawaiʻi. Discoveries like these particularly speak to the importance of undergraduate research experience, international collaboration, and building longstanding relationships that allow these discoveries to occur.

This study is a culmination of over two decades of collaboration between researchers at CFHT and Laval. R. Pierre Martin, the principal investigator, former astronomer, and director of science operations at CFHT, who is now the chair of the Department of Physics and Astronomy at UH Hilo and director of the UHH Educational Observatory. He and Laurent Drissen, the third author listed in the study, actually first met on Maunakea. “Maunakea brought us together as a research team. It is a very special place for Hawai‘i and for the world. There are many researchers worldwide who really, deeply care about Maunakea,” said Pierre.  

Their ongoing work together began with a dream — to build an instrument capable of observing all sorts of galaxy phenomena and behavior over a much larger field of view than was previously possible. Perhaps even large enough to observe multiple galaxies in their entirety. After many years of incredibly hard work led by Laurent, the instrument came to fruition in 2015 — the Fourier Transform spectrograph SITELLE, installed at CFHT. “It’s a remarkable instrument,” said Pierre. “Among all the galaxies we have been studying since, notably under a large program called SIGNALS, I've also wanted to study this specific galaxy collision for a long time. But we never had the right instrument until now.” With its exceptional capabilities, SITELLE was able to capture the entirety of both galaxies at once, allowing researchers to model the full extent of the collision in dazzling detail. 

The collision in question began ~440 million years ago, between two large galaxies called NGC 2207 and IC 2163. Since then, the two have slammed into each other, pulled apart, and come back together multiple times. Eventually they will merge into one, and their ancient shapes and characteristics will be rendered unrecognizable. 

“All galaxies collide in their lifetimes. They are very social beings!” Pierre explained. The immense gravity pulls galaxies towards one another, and these interactions range from small ones — like when the Milky Way has eaten up small galaxies in the past — to completely transformative. The research team hoped to not only try to understand the collision but also how it has altered both galaxies and how it may continue to in the future. 

This particular galaxy collision was first simulated 20 years ago by other investigators. The team used these early models to create a starting point for their own simulation, which was carried out using advanced, high-performance computer simulations based at Université Laval in Québec. They ran hundreds of simulations, using the high-quality data from the SITELLE spectrograph to model the shape, gas distribution, rate of star formation, and the motions of stars and gases throughout the galaxies with great accuracy. “This is the most sophisticated simulation to do this in the world right now,” Pierre said. By simulating both how the galaxies would have evolved individually as well as simulating collisions until they finally matched our contemporary observations, the team was able to create an impressive model that spans more than 600 million years – from their first interaction 440 million years ago to predicting the galaxies’ behavior more than 200 million years into the future. 

Making those predictions can be extremely difficult, as every collision is unique. “It’s as if you said, ‘model a car crash,’” explained Pierre. The number of variables — speed, angle, the makeup of elements in the galaxies — means there is an almost infinite range of what galactic collisions can look like. But studying one in detail, like NGC 2207 and IC 2163, gives us a better idea of what could happen in the future, including for our own galaxy, the Milky Way. When galaxies collide, it can have a big ripple effect, literally, which redistributes the gases and chemical elements within the galaxies. These gas cloud collisions can often trigger more new star formations, as the increased mixing of gases between the two galaxies introduces new elements that may have been missing. This has large consequences for the galaxy’s evolution as well as kinds of new planets that then form within the galaxy. 

It All Started With a Summer Internship…

The team based in Québec — Camille Poitras, Laurent Drissen, Hugo Martel, and Carmelle Robert — was responsible for developing the tools necessary to accomplish this discovery, as well as much of the simulation and analysis. As the project developed, they brought in additional collaborators to strengthen the team’s expertise, Camille explained. Carmelle’s knowledge of star-forming regions and Hugo’s experience in creating simulations over time, like the one above, rounded out the team’s understanding of the collision over time and present-day observations. Camille credited that many of the collaborators are used to working together on projects like these. “Their prior experience collaborating made it very easy for me to integrate into the group and contribute effectively,” she said.

Pierre was quick to highlight that Camille, the lead author, was responsible for most of the work encapsulated in this paper, which she began as an undergraduate student two years ago at Laval. She is now 23 years old and the recipient of numerous astronomy awards, including first place at Laval’s undergraduate research symposium and a medal from the Lieutenant Governor of Quebec for her academic and community work in 2015. She is currently pursuing her PhD at Université Laval. Her first experience in astrophysics research, through a summer internship with Laurent Drissen, confirmed that she wanted to pursue astronomy further. At that time Laurent and Pierre, who have collaborated for many years, were putting together a project using the world-class data from CFHT’s SITELLE spectrograph and brought Camille on board.

Undergraduate research is increasingly being recognized as an invaluable opportunity for students to develop skills and gain hands-on experience in astronomy. Camille credits her early engagement in research as having a significant impact on her academic path. “It helped me develop a more independent and critical approach to problem-solving,” she said. It’s also an invaluable chance to explore different fields before committing to a specific focus, she continued. 

What is the most important skill that students might master through research? In Pierre’s opinion, “perseverance.” Research teaches students the ability to persist and persevere, despite the lengthy process and the many setbacks or dead ends they may encounter along the way. 

And with this team, persevere they did. They built their dream instrument from scratch over the past decade, and thanks to its massive field of view, they observed 20 times as many star-forming regions as any previous studies. “It took us more than two years to analyze the data, then to investigate the collision with the simulations, and then to write the paper!” Pierre recounted. These questions and projects won’t be solved quickly. But, he explained, this is an essential part of training as a student — to dig in to the hard work and stick with it. “It’s only when you do it that you really learn.” 

Telescope and lab time have become a central pillar of UH Hilo’s astronomy program for precisely that reason — to give undergrad students the opportunity to learn in a hands-on approach. Every astronomy lecture at UHH has a lab that gets students visiting telescopes, engaging with MKO scientists, and potentially getting observation time on Maunakea. “Even if you’ve never touched a telescope before in your life, for the four years you have here, it’s all about hands-on experience.” Involving students in research has become an integral part of their curriculum. UHH formalized this mission in a 2017 memorandum, which now requires that every proposal for observing time that they submit to telescopes must include undergraduate students on the research team. 

This approach encourages students to see the entire process of doing science, from project proposal to observation to analysis to publication. Not only do they learn how to problem-solve and think on their feet, but students also graduate with valuable, concrete skills they can put to use in their future careers, notably in observatories — whether here or on the mainland. “It’s very important to us that students who are from here get to stay if they want to,” Pierre said. “And we also have students who are very successful on the mainland, from space programming to even operating cameras on Mars rovers.” 

In the case of this study, undergraduate research blossomed into a unique publication from a team with thousands of miles between them. “International collaboration is essential in astronomy,” Camille said, and this work often requires “collaborative efforts that go beyond a single institution or country.” Pierre echoed the sentiment, saying, “It’s all about the group working together over long distances, led by this amazing young woman.” The MKOs are proud to work with the bright young scholars who are forging the way for the future of astronomy.